Arctic Greenhouse

Reconstructing Ancient Landscapes and Ecosystems

September 17, 2015

1544

By Claudia Schröder-Adams

The Arctic summer holds many surprises; unpredictable weather can change flight conditions at a moment’s notice. We are in Resolute Bay, an Inuit hamlet on Cornwallis Island and home to the logistical headquarters of the Polar Continental Shelf Program. Here we start the journey that will bring us to Axel Heiberg and Ellesmere islands to investigate how the Arctic has responded to past greenhouse phases throughout the Earth’s climatic history. Skies over our planned landing spot at the southern tip of Axel Heiberg Island are clearing and we have the green light to lift off during snowfall in Resolute. Our Twin Otter is loaded with enough gear that will allow us to stay out on the remote islands for the next four weeks. The excitement is rising!

The mission of our expedition is well defined. My team worked here in 2011 and now we return to find the answers to our specific questions. Throughout Earth’s history, past ecosystems had to cope with catastrophic events, which either brought mass extinctions of species or new adaptations, depending on duration and severity. These events were not caused by human activity, as our species was not yet around. Widespread biotic decline was caused by geological processes such as extreme sea-level fluctuations, periods when oceans become devoid of oxygen, and massive volcanic eruptions, to name a few. The latter are marked by the rise of huge masses of molten magma from the Earth’s interior onto either a continent or ocean floor, called LIPs or Large Igneous Provinces. The Cretaceous Period covering earth history from 145 to 66 million years ago was an especially dynamic time, where a multitude of processes were at work. We are interested to discover what the feedback mechanisms of these processes were and how the polar region responded to those extreme events.

As we fly North, mainly above cloudy skies, we arrive at Sherwood Head at the mouth of Glacier Fiord on the southern tip of Axel Heiberg Island. This island is uninhabited by humans with the exception of a McGill University research station which came kindly to our rescue during one of our camp moves when we got caught in bad weather. Due to uneven terrain at our final destination, the Twin Otter will deliver us here at the mouth of the fiord where we wait for the helicopter coming from Eureka. As the pilots leave us, we begin to grasp the immensity of these Arctic landscapes, the overwhelming and welcome stillness of this land and the intricacies of Arctic flora surrounding us. These small plants cling to the rocky ground and their full beauty stuns, despite a short blooming season.

Small microscopic life, so often overlooked, delivers the best indicators for past environmental change. These are now microfossils within abundant sediments oen widely distributed allowing for large-scale correlations. The analysis of their shells allow for the reconstruction of geochemical oceanic conditions. Understanding how past marine communities have responded to catastrophic events during the Cretaceous allows us to better predict the response of future oceans to a warming earth. The Glacier Fiord region has superb exposures of the entire Cretaceous Period, which enables us to perform high-resolution sampling and ultimately the reconstruction of ancient landscapes and their ecosystems. Our results from previous fieldwork had identified times of large emissions of volcanic CO2, unusual warm temperatures for a polar region and phases of depleted oxygen in this ancient ocean. We need to understand if those events might be caused by the eruption of the High Arctic Large Igneous Province (HALIP).

My trusted team consists of Jens Herrle (Goethe University, Frankfurt, Germany), specialist in the earth ancient carbon cycle; my graduate student Alex Quesnel who is interested in the big picture by correlating between several Arctic basins; and Keenan Lindell, videographer and environmental science student in Iqaluit. Keenan’s extensive video footage chronicling our expedition will form the basis of a nature documentary entitled, ‘Arctic Greenhouse’ to be released in September 2015.

This summer Glacier Fiord is still frozen. In front of us lies the Steacie Icefield. Valleys on both sides of the fiord are occupied with piedmont glaciers that spill onto the coastal region. I look down from the helicopter and have the bird’s-eye view of the sediments along both shores that were deposited in a Cretaceous marine basin that covered a large part of the High Arctic Islands. Land, which is now islands, was once ocean 110 to 80 million years ago telling a story of fluctuating sea levels and tectonic movement through geological time. A sedimentary basin preserves ancient sediments, which carry the evidence from past environments. This basin is named the Sverdrup Basin in honour of the Norwegian Explorer Otto Sverdrup who charted 260,000 square kilometres of Arctic islands in the late 1800s.

As we circle over our camp, we spot a herd of muskox grazing along surrounding slopes. These majestic animals keep their distance, but remain welcoming neighbours during our work at Glacier Fiord. Nevertheless, we seem to feel like the intruders in their habitat and home. As the helicopter leaves, a longed-for silence sets in and we get to work setting up camp beside a large glacier. Its melting history is starkly obvious by the large boulder fields at its front, forming the end moraine, and a melt water river that significantly swells during the days as the sun gains energy. This melt is also our source for delicious drinking water. The kitchen and sleeping tents are set up, complete with a radio antenna for our daily communication with the Polar Continental Shelf.

Now we are ready to investigate how the ancient ocean that surrounds us in the form of sedimentary exposures reacted to unusual greenhouse conditions 105 to 90 million years ago. This was an extreme time where tropical sea surface temperatures reached 35°C and in Polar Regions up to 20°C. Modern Arctic sea surface temperature ranges from freezing to about 7°C with a measurable warming trend in recent years. In the Cretaceous, production of increased greenhouse gases in the atmosphere accelerated through phases of intense volcanism coupled with plate tectonic activity during that time. Oceans such as the Atlantic kept on growing, pushing North America westward. This caused plate collisions along the Pacific margin and abundant volcanism, sending huge ash clouds into the atmosphere, which then settled down into the ocean sediments. The Arctic Ocean also started to form and intraplate magmas caused by melting in the Earth’s mantle resulted in continental flood basalts and volcanic eruptions. Our previous work allowed us to pinpoint the sediment exposure that documents the Sverdrup Basin’s response to this unique phase. To understand the exact timing and how ecosystems responded, we need to go back to sample in more detail.

After a week’s hard work at this locality we fly further inland along the Steacie Icefield to reach another locality where we want to investigate the early Cretaceous. As the helicopter picks us up and Keenan and I are the first to move out, I think of previous explorers who would have travelled by dog team or small fixed-wing aircraft and often stayed for several months at a time. Their impressive work forms the fundamental base for what we do.

Our next destination is Lost Hammer Diapir and we wonder if there is a tool to be found! The magnificence of this locality easily distracts us from keeping a sharp eye out for a reliable freshwater source as we circle over a possible camp spot. I am overwhelmed by the majestic landscape. Here we hike every day to the Lower Cretaceous Deer Bay Formation that also carries an interesting climatic signal. Not to miss short-lived extreme processes that mark this phase of the Polar Sea, we sample in great detail, carrying heavy backpacks on a long uphill trek every night to make it back to camp.

One evening we climb onto a ridge and an amazing sight reveals the entire Cretaceous Period with all its changes in front of our eyes. This history of nearly 80 million years encompasses several kilometres of sedimentary strata. We clearly make out the Strand Fiord volcanic basalt flow, which forms one phase of the HALIP, as it sticks out as a black band within lighter coloured sediments. This is why working in the Arctic as a geologist is rewarding beyond belief. There are not many spots on Earth where you see, unobstructed, an entire geological period in front of your eyes. Working here feels like a tremendous privilege.